Bull. Earthq. Res. Inst. Vol. 2 ... - University of Tokyo · Development of the 1./-arc-second Engineering Geomor-phologic Classification Database and its Application to Seismic

Development of the 1./-arc-second Engineering Geomor-

phologic Classification Database and its Application to

Seismic Microzoning

Kazue Wakamatsu+�� ,�* and Masashi Matsuoka-�

+� Kawasaki Laboratory, Earthquake Disaster Mitigation Research Center, NIED, Kawasaki ,+*-***0, Japan

,� Center for Urban Earthquake Engineering, Tokyo Institute of Technology, Yokohama ,,0-2/*,, Japan

-� Earthquake Disaster Mitigation Research Center, NIED, Kobe 0/+-**1-, Japan

Abstract

In a seismic hazard assessment, local geologic and ground conditions play important roles in

characterizing and estimating hazards. We developed a systematically standardized GIS-based

ground-condition map containing the attributes of geomorphologic classification in grid cells of 1./

arc-seconds latitude�++.,/ arc-seconds longitude for several areas including major urban areas in

Japan. This paper introduces the concept of developing the 1./-arc-second JEGM, (Japan Engineer-

ing Geomorphologic Classification Map) and presents sample images of the JEGM. As an example

of the database’s application to estimating the hazards�the average shear velocity of the ground in

the upper -* m,�Vs-* is estimated and mapped for the Kanto area, and the distribution of peak

ground velocities (PGV) for the Great +3,- Kanto earthquake is estimated using the Vs-* map and

empirical formulae. The computed PGV distribution agrees well with the distribution of seismic

intensities evaluated from damage to wooden houses for areas located far from the earthquake fault.

However, it will be necessary to calculate ground motion based on an asperity model to evaluate

near-fault regions.

Key words� GIS database, geomorphologic classification, seismic hazard mapping, Vs-*, PGV

+. Introduction

Several major earthquakes including the Tokai,

Tonankai and Nankai earthquakes are expected to

occur with high probabilities in the near future in

Japan. Local ground conditions play important roles

in characterizing and assessing their hazards. How-

ever, neither a digital database nor paper maps of

ground conditions throughout Japan had been avail-

able in a unified form.

Therefore, the authors have created a systemati-

cally standardized GIS-based ground-condition map

covering all of Japan, the “Japan Engineering Geo-

morphologic Classification Map (JEGM)” (Wakamatsu

et al. ,**.), which was released in November ,**/

(Wakamatsu et al., ,**/). The database covers all of

Japan with a Japanese standard size grid, which is -*

arc-seconds latitude�./ arc-seconds longitude (ap-

proximately +�+ km,) and includes five sets of major

attributes�geomorphologic classification, geologic

age, slope angle, elevation, and relative relief�in

approximately -2*,*** grid cells. Among its attrib-

utes, the geomorphologic classification database was

based on a new engineering-based geomorphologic

classification scheme for identifying and classifying

subsurface ground conditions.

The JEGM was employed for the following types

of nationwide hazard mapping : liquefaction poten-

tial (Wakamatsu et al. ,**.), average shear velocity

of ground in the upper -* m, Vs-*, for estimating the

site amplification factors (Matsuoka et al., ,**/), flood

potential (Wakamatsu et al., ,**/), and erosion rate

potential in mountainous area (Hasegawa et al., ,**/ ;

Hasegawa et al., ,**0a).

To perform more accurate hazard zoning, we

� � � � �Bull. Earthq. Res. Inst.

Univ. Tokyo

Vol. 2+ �,**0� pp. -+1�-,.

* e-mail : [email protected]

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have been developing a 1./-arc-second Japan Engi-

neering Geomorphologic Classification Map (1./-arc-

second JEGM) for major areas in Japan, which is a

high spatial-resolution version of the above-mentioned

-*-arc-second JEGM. In this paper, we present the

concept behind the development of the 1./-arc-second

engineering geomorphologic classification database

(the 1./-arc-second JEGM) and its application for seis-

mic hazard estimation.

,. 1./-arc-second JEGM

�+� Concept of Mapping

The map contains an attribute of geomorpho-

logic classification in grid cells that are 1./ arc-

seconds latitude�++.,/ arc-seconds longitude (ap-

proximately ,/*�,/* m,) in size. The criteria for -*

arc-second JEGM were used to develop the 1./-arc-

second JEGM, with some additional classifications

such as “lowland between coastal dunes and/or bars,”

“rock shore, rock reef,” and “dry river bed,” which are

negligible areas in the +-km square grid cell. A

description of geomorphologic map units is pre-

sented in Table +, together with the corresponding

general ground conditions and general depth of

groundwater. These criteria were based on the pur-

pose of the mapping project : identification and clas-

sification of subsurface ground conditions, through

standard geomorphologic classification.

The geomorphologic factors presented in Table

+ are known to be correlated with subsurface ground

and hydrologic conditions (e.g. Zuidam et al., +320).

Figure + shows, for example, typical profiles of bor-

ing log, SPT N-values, and elastic wave velocities for

three geomorphologic units consisted of sandy soils :

marine bar, dune, and natural levee. The profiles are

significantly di#erent based on geomorphologic process

and/or sedimentary environment of each unit : ma-

rine bar generally consisted of moderately dense to

dense sands and/or gravelly sands associated with

higher N-value and faster elastic wave velocity ;

dune formed by aeolian processes consisted of loose

fine to medium sands associated with low N-value

and slow elastic wave velocity, which is usually un-

derlain by dense marine bar deposits ; and natural

levee formed by fluvial processes was composed of

loose sandy soil which was generally underlain by

soft fluvial and/or marine cohesive soils.

These are the results of bar deposits compacted

under dynamic loading by ocean waves and coastal

currents. By contrast, dune and levee deposits accu-

mulate loosely on the wind and river flow, respec-

tively. These geomorphologic factors therefore di-

rectly or indirectly influence the subsurface geotech-

nical ground conditions, although there are some

di#erences based on regionality.

�,� Procedure of Mapping

First, the preliminary map was compiled ; the

major geomorphologic units were evaluated and

classified on the basis of the -*-arc-second JEGM and

interpretation of topographic maps. The detailed

geomorphologic surveys of local geomorphologic

features at scales of + : /*,*** were subsequently per-

formed to delineate units on the basis of the criteria

listed in Table +, based on interpretation and compi-

lation of existing information, which is available

from published reports, papers, topographical maps,

and other available maps and boring exploration

data, in addition to our expertise in geomorphology

and geotechnical engineering. Finally, a detailed map

was drawn up, and digitized and stored in cells using

GIS software. Each cell is assigned to the single

geomorphologic unit that occupies the greatest area

of the cell when multiple units exist within the cell.

Figures , shows the areas for which the 1./-arc-

second JEGM is already constructed ; areas of Sap-

poro, Sendai, Kanto including Tokyo, Chukyo includ-

ing Nagoya, Kinki including Osaka, Kyoto, and Kobe,

and Nankaido including Hiroshima, Okayama, and

Matsuyama. Sample images of the 1./-arc-second JEGM

for these areas are shown in Figures . to 3, respec-

tively. The legend for these maps is shown in Figure

-. The total number of cells of these maps is approxi-

mately ,,./1,***, which cover nearly .*� of Japan.

-. Utilization of 1./-arc-second JEGM for Seismic

Hazard Estimation

The 1./-arc-second JEGM has been used for esti-

mating the average shear velocity of the ground in

the upper -* m, Vs-*, amplification factors of peak

ground velocities and liquefaction potential for the

a#ected area of the ,**. Niigata-ken Chuetsu earth-

quake (Wakamatsu and Matsuoka, ,**0), and overlay

analysis of water supply pipes damaged by the earth-

quake (Hasegawa et al., ,**0b).

In this paper, we present a Vs-* mapping of the

Kanto area and distribution of peak ground velocity

K. Wakamatsu and M. Matsuoka

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Table +. Description of geomorphologic map units in the 1./-arc-second JEGM.

Development of the 1./-arc-second Engineering Geomorphologic Classification Database and its Application to Seismic Microzoning

� 319�

(PGV) for the +3,- Kanto earthquake estimated based

on the Vs-* map.

In a previous study (Matsuoka et al., ,**0), we

calculated the Vs-*, which is a simple and useful

predictor for estimating the site amplification factors

of strong ground motions, covering approximately

,,*** sites all over Japan where shear-wave velocity

has been measured. Geomorphologic units for all PS

logging data sites were interpreted using the original

data of the JEGM. Next, we examined the correlation

between not only geomorphologic units but also geo-

graphical information derived from the JEGM and

the Vs-* values. We found that the Vs-*s showed

some dependency on altitudes, slopes, and distances

from mountains or hills formed during older periods

(Pre-Tertiary or Tertiary). A multiple linear regres-

sion formula for each geomorphologic unit was de-

veloped to estimate the Vs-* using elevation (Ev),

slope (Sp), and distance (Dm) from a mountain or a

hill as explanatory variables. The basic regression

formula is the following equation :

log VS-*�a�b log Ev�c log Sp�d log Dm�s

�

where a, b, c, and d represent regression coe$cients,

and s is the standard deviation. The units of Ev, Sp,

and Dm are meters, +*** times tangent values, and

kilometers, respectively. When the value of the ex-

planatory variable is less than +, we fixed the value

as “+.”

Table , shows the regression coe$cients and

standard deviation of each geomorphologic unit ob-

tained by regression analysis. The regression co-

e$cients show that the higher the elevation, the

steeper the slope, and the shorter the distance from

the mountain or the hill, Vs-* values become larger.

As for the logarithmic standard deviation for the

overall estimation, the estimation formula shown in

Equation + has a higher accuracy than previous em-

pirical estimations (Matsuoka et al., ,**0). Using

Equation + and the attributes of the geomorphologic

classification in the 1./-arc-second JEGM, geologic

age, elevation, and slope contained in the -*-arc-

second JEGM, we were able to compute the Vs-*

distribution with ,/* m spatial resolution.

Figure +* shows the Vs-* map for the Kanto

area. The Vs-* values are approximately +/* m/s on

delta and coastal lowland, reclaimed land, and back

marsh. The areas of valley bottom lowland also show

a rather small Vs-* in the range from +2* to ,** m/s.

To indicate the advantage of the proposed high-

resolution Vs-* estimation, the comparison with the

previous Vs-* map, which was derived from the -*-

arc-second JEGM, is shown in Figure ++. The high-

resolution geomorphologic classification of the 1./-

arc-second JEGM enables complicated outlines of

geomorphologic map units such as abandoned river

channels, natural levee, and valley bottom lowland

to be traced. This allows a more realistic Vs-* distri-

bution to be created, as shown in Figure ++ (a).

Fig. +. Typical profiles of boring log, SPT N-values,

and elastic wave velocities for three geomorphologic

units comprised of sandy soil (Wakamatsu et al., ,**. ;

Borehole data source : National Research Institute for

Earth Science and Disaster Prevention, +331)

Fig. ,. Areas for which the 1./-arc-second JEGM is

constructed.

K. Wakamatsu and M. Matsuoka

� 320�

Fig. /. 1./ arc-second JEGM for Sendai area. Fig. 2. 1./ arc-second JEGM for Kinki area.

Fig. 1. 1./ arc-second JEGM for Chukyo area.Fig. .. 1./ arc-second JEGM for Sapporo area.

Fig. 0. 1./ arc-second JEGM image for Kanto area.Fig. -. Geomorphologic Classification in the 1./-arc-

second JEGM (legend for Figures . to 3)

Development of the 1./-arc-second Engineering Geomorphologic Classification Database and its Application to Seismic Microzoning

� 321�

Fig. 3. 1./ arc-second JEGM for Nankaido area.

Fig. +,. PGV site amplification map converted from

Vs-* map

Fig. +-. PGV potential map for the +3,- Great Kanto

earthquake using 1./-arc-second JEGM

Fig. +.. Distribution of seismic intensity of the +3,-

Great Kanto earthquake evaluated from distribution of

ratio of collapsed wooden houses (Moroi and Takemura,

,**,)

Fig. +*. Vs-* map calculated from the 1./-arc- second

JEGM for the Kanto area.

Fig. ++. Zoom-in images (rectangle area in Fig. +*) of

Vs-* map for central Kanto area. (a) calculated from

the 1./-arc- second JEGM. (b) calculated from the -*-

arc- second JEGM.

K. Wakamatsu and M. Matsuoka

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To draw an amplification capability map, the Vs

-* was converted into the amplification factor for

PGV with respect to sti# soil, which corresponds to

ground with Vs-* of 0** m/s, through an empirical

relationship (Fujimoto and Midorikawa, ,**0). The

amplification map for the Kanto area is shown in

Figure +,.

The potential for ground motion was obtained

by multiplying the amplification capability into ground

motion intensity on sti# soil. Figure +- shows the

PGV potential map for the +3,- Great Kanto earth-

quake (Mw 1.3) using 1./-arc-second JEGM. In this

estimation, the location of the earthquake fault refers

to the results of Kanamori (+31+), and the PGV on sti#

soil was simply estimated from an attenuation rela-

tionship proposed by Si and Midorikawa (,***). Fig-

ure +. shows the distribution of seismic intensities of

the +3,- Great Kanto earthquake evaluated from the

distribution of ratios of collapsed wooden houses.

For a macroscopic point of view, the areas were

located some distance from the earthquake fault, and

the computed PGV distribution is in quite good

agreement with the distribution of seismic intensi-

ties evaluated from damage to wooden houses. To

evaluate near-fault regions, it will be necessary to

calculate ground motion based on an asperity model.

.. Conclusion

In this study, we introduce the 1./-arc-second

“Japan Engineering Geomorphologic Classification

Map (JEGM),” the high spatial-resolution version of

-*-arc-second JEGM, which was based on engineer-

ing-based geomorphologic classification standards ;

the concept and procedure of mapping are described,

and the image samples of 1./-arc-second JEGM for

major urban areas in Japan are presented.

As an example of the database’s application to

detailed and accurate hazard zoning, we estimated

and mapped the average shear-wave velocity of the

ground in the upper -* m, Vs-* for the Kanto area.

Finally, we present detailed maps of amplification

capability for peak ground velocity (PGV) in the area

and PGV potential estimation for the +3,- Great

Kanto earthquake using the Vs-* map and empirical

relationships. The computed PGV distribution is in

quite good agreement with the distribution of seis-

mic intensities evaluated from damage to wooden

houses for areas located some distance from the

earthquake fault. However, it will be necessary to

calculate ground motion based on an asperity model

to evaluate the near-fault regions.

Acknowledgments

The work presented in this paper was supported

Table ,. Regression coe$cient obtained by regression analysis (Matsuoka et al., ,**0)

Development of the 1./-arc-second Engineering Geomorphologic Classification Database and its Application to Seismic Microzoning

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by the Special Project for Earthquake Disaster Miti-

gation in Urban Areas from the Ministry of Educa-

tion, Culture, Sports, Science and Technology of Ja-

pan. The authors gratefully acknowledged this sup-

port. They also thank Prof. S. Midorikawa, Tokyo

Institute of Technology for providing us facilities for

this research.

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(Received December /, ,**/)

(Accepted January +0, ,**1)

K. Wakamatsu and M. Matsuoka

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